This invention relates to scanning apparatus disposed in a vacuum system in general and more particularly to a flat camera or display device for use in television systems.
In one known image pickup tube of a television camera, the image picked up by an objective lens is converted into electrical signals. The tube contains an image converter part which generates an electric charge image from the optical image, by means of a photo cathode or a semiconductor layer, which is stored in a storage plate of the image converter. In an adjacent scanning arrangement, the storage plate is scanned by an electron beam. The scanning beam is controlled by the same clock generator which also furnishes the synchronizing pulses. A load resistor is connected into the circuit of the scanning beam as an electronic component. The voltage drop of load resistor is determined by the electron current of the scanning beam and the video signal is taken off this resistor. Since the image converter and the scanning device are connected in series in the direction of the signal flow and a certain minimum depth is necessary for scanning with an analog-controlled electron beam, a flat arrangement cannot be obtained with this design.
In one known display device, a thermal cathode and a hole matrix with an electrode arrangement for row and column control, as well as the picture screen, are arranged in a vacuum chamber. This display device contains electrodes which can be driven by binary signals and which are arranged in 18 planes parallel to and one behind the other, for instance, for controlling 512.times.512 picture elements. The electrodes of the individual planes are separated from each other by insulating planes which contain holes, assigned to individual picture elements, for the electron stream. The electrodes comprise conducting strips arranged on the hole plate. They are likewise provided with holes assigned to individual picture elements. The electrodes of the individual planes are tied together in groups and are provided with common control leads. Of the 18 electrode planes, 9 are provided for row control and 9 for column control. The large number of electrode planes and the insulating layers arranged between them produce a relatively thick control arrangement. A long path for the electrons which are released from the cathode and are accelerated in a direction toward the anode, in the canals which are formed by the matrix holes in tandem and are associated with the individual picture elements, is thus brought about (IEEE Trans. on Electron Devices, vol. ED-20, no. 11, Nov. 1973, pages 1052-1061).